Semiconductor Device

ABSTRACT

To solve a problem in that an antenna or a circuit including a thin film transistor is damaged due to discharge of electric charge accumulated in an insulator (a problem of electrostatic discharge), a semiconductor device includes a first insulator, a circuit including a thin film transistor provided over the first insulator, an antenna which is provided over the circuit and is electrically connected to the circuit, and a second insulator provided over the antenna, a first conductive film provided between the first insulator and the circuit, and a second conductive film provided between the second insulator and the antenna.

TECHNICAL FIELD

Technical field relates to semiconductor devices including antennas.

BACKGROUND ART

In order to realize ubiquitous computing, semiconductor devices forperforming wireless communication through antennas (also referred to asRFID tags, wireless tags, IC chips, wireless chips, noncontact signalprocessing devices, or semiconductor integrated circuit chips) havedeveloped (for example, see Reference 1).

REFERENCE

Reference 1: Japanese Published Patent Application No. 2007-005778

DISCLOSURE OF INVENTION

In a semiconductor device for performing wireless communication throughan antenna, in order to protect the antenna and a circuit including athin film transistor, the antenna and the circuit including the thinfilm transistor are interposed between epoxy resins or the like.

However, insulators such as epoxy resins easily accumulate electriccharge.

Therefore, due to discharge of electric charge accumulated in aninsulator, there has been a problem in that the antenna or the circuitincluding the thin film transistor is damaged (a problem ofelectrostatic discharge).

In view of the forgoing problem, the invention for solving the problemof electrostatic discharge is disclosed.

In a semiconductor device having a structure where an antenna and acircuit including a thin film transistor are interposed between a pairof insulators, at least one conductive film is formed outside or insidethe pair of insulators so that electrostatic withstand voltage isincreased. Thus, electrostatic discharge can be suppressed.

Note that the antenna is provided with an interlayer insulating filmwhich covers the circuit including the thin film transistor interposedbetween the antenna and the circuit including the thin film transistor.

According to the results of an experiment performed by the presentinventors, it is found that electrostatic discharge is generated moreeasily in the case where voltage is applied from a thin film transistorside as compared to the case where voltage is applied from an antennaside.

Thus, the conductive film is preferably provided on the thin filmtransistor side.

Further, according to the results of the experiment performed by thepresent inventors, it is found that electrostatic withstand voltage onthe antenna side is increased by providing a conductive film on theantenna side.

Thus, the conductive film is preferably provided on the antenna side.

That is, by providing the conductive films on both the thin filmtransistor side and the antenna side, electrostatic withstand voltagewith respect to the application of voltage on both sides is increased.

Thus, the conductive films are preferably provided on both the thin filmtransistor side and the antenna side.

In particular, in the case of a semiconductor device for transmittingand receiving radio waves from both surfaces regardless of a frontsurface and a rear surface, such as a wireless IC card used for anautomatic ticket gate at a station, which has been widely used in recentyears, conductive films are preferably provided on both a thin filmtransistor side and an antenna side.

Note that in the case where a conductive film is provided outside thepair of insulators, the conductive film is exposed.

Then, after using the semiconductor device a number of times, theexposed conductive film might be peeled due to friction or the like, sothat an effect of preventing electrostatic discharge might besignificantly decreased.

Thus, by providing a conductive film inside the pair of insulators, theconductive film can be protected by the pair of insulators. Needless tosay, a conductive film may be provided outside the pair of insulators,or conductive films may be provided both outside and inside the pair ofinsulators.

Note that a problem of peeling of the conductive film due to friction orthe like is a problem caused due to the film-shape of a conductor. Sucha problem is not caused in the case where a conductor having sufficientthickness (e.g., a conductive substrate) is used.

Further, when a conductive film is provided on an outer side than theantenna, a problem of decrease in resonant frequency in no small partdue to the conductive film is caused. When the decrease in resonantfrequency is large, a problem of decrease in communication distance iscaused.

Thus, by providing a conductive film between the antenna and the circuitincluding the thin film transistor, the antenna is exposed. Accordingly,the problem of decrease in resonant frequency due to the conductive filmcan be solved.

In addition, in the case where conductive films are provided on both theantenna side and the thin film transistor side, both the conductivefilms are electrically connected to each other. Thus, an adverse effectof electrostatic discharge due to dielectric polarization can bereduced, which is preferable.

That is, a semiconductor device which is formed as follows ispreferable. A first insulator, a circuit including a thin filmtransistor provided over the first insulator, an antenna which isprovided over the circuit and is electrically connected to the circuit,and a second insulator provided over the antenna are provided; a firstconductive film is provided between the first insulator and the circuit;a second conductive film is provided between the second insulator andthe antenna.

In addition, a semiconductor device which is formed as follows ispreferable. A first insulator, a circuit including a thin filmtransistor provided over the first insulator, an antenna which isprovided over the circuit and is electrically connected to the circuit,and a second insulator provided over the antenna are provided; a firstconductive film is provided between the first insulator and the circuit;a second conductive film is provided between the circuit and theantenna.

Note that each of the first insulator and the second insulatorpreferably has a structure where a fibrous body is impregnated with anorganic resin. In addition, the first conductive film and the secondconductive film are preferably electrically connected to each other.

In a semiconductor device having a structure where an antenna and acircuit including a thin film transistor are interposed between a pairof insulators, at least one conductive film is formed outside or insidethe pair of insulators so that electrostatic withstand voltage can beincreased.

In addition, by providing a conductive film inside the pair ofinsulators, the conductive film can be protected by the pair ofinsulators. Thus, a film-shaped conductor (conductive film) can beprevented from being peeled due to friction or the like.

In addition, in the case where conductive films are provided on both anantenna side and a thin film transistor side, both the conductive filmsare electrically connected to each other. Thus, an adverse effect ofelectrostatic discharge due to dielectric polarization can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIG. 1 illustrates an example of a semiconductor device;

FIG. 2 illustrates an example of a semiconductor device;

FIGS. 3A to 3F illustrate examples of semiconductor devices;

FIGS. 4A and 4B illustrate an example of a method for manufacturing asemiconductor device;

FIGS. 5A and 5B illustrate an example of the method for manufacturing asemiconductor device;

FIG. 6 illustrates an example of the method for manufacturing asemiconductor device;

FIG. 7 illustrates an example of the method for manufacturing asemiconductor device;

FIGS. 8A and 8B illustrate an example of a method for manufacturing asemiconductor device;

FIG. 9 illustrates an example of the method for manufacturing asemiconductor device;

FIG. 10 illustrates an example of the method for manufacturing asemiconductor device;

FIG. 11 illustrates an example of a semiconductor device;

FIG. 12 illustrates an example of a semiconductor device;

FIG. 13 illustrates an example of a semiconductor device;

FIG. 14 illustrates an example of a semiconductor device;

FIG. 15 illustrates an example of a semiconductor device;

FIG. 16 is a top view of a prepreg;

FIGS. 17A to 17G illustrate comparison between structures manufacturedin Example 1;

FIG. 18 illustrates an example of a circuit diagram; and

FIG. 19 illustrates measurement results in Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments and examples will be described in detail with reference tothe drawings.

Note that it will be readily appreciated by those skilled in the artthat the disclosed invention is not limited to the following descriptionand that modes and details of the disclosed invention can be changed invarious ways without departing from the spirit and scope of thedisclosed invention.

Therefore, the disclosed invention should not be construed as beinglimited to the following description of the embodiments and examples.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated.

Embodiment 1

In this embodiment, the structure of a semiconductor device isdescribed.

A semiconductor device of this embodiment includes a structure where afirst insulator formed using a fibrous body 102 impregnated with anorganic resin 101, a first conductive film 103, a first insulating film104, a layer 105 including a circuit having a thin film transistor, alayer 106 including an antenna, a second insulating film 107, a secondconductive film 108, and a second insulator formed using a fibrous body110 impregnated with an organic resin 109 are sequentially stacked (seeFIG. 1).

Note that the antenna is electrically connected to the circuit havingthe thin film transistor with an interlayer insulating film interposedtherebetween.

As each of the organic resin 101 and the organic resin 109, athermosetting resin, a thermoplastic resin, or the like can be used.

As a thermosetting resin, an epoxy resin, an unsaturated polyesterresin, a polyimide resin, a bismaleimide triazine resin, a cyanateresin, or the like can be used.

As a thermoplastic resin, a polyphenylene oxide resin, a polyetherimideresin, a fluoropolymer, or the like can be used.

By using a thermosetting resin or a thermoplastic resin,thermocompression bonding is possible. Thus, manufacturing steps can besimplified, which is advantageous.

In addition, each of the fibrous body 102 and the fibrous body 110 is awoven fabric or a nonwoven fabric.

A woven fabric is a cloth-shaped material obtained by weaving aplurality of fibers.

A nonwoven fabric is a cloth-shaped material obtained by performingfusion bonding, adhesive bonding, twisting, or the like on a pluralityof fibers without weaving the plurality of fibers.

As a fiber, a polyvinyl alcohol fiber, a polyester fiber, a polyimidefiber, a polyethylene fiber, an aramid fiber, a polyparaphenylenebenzobisoxazole fiber, a glass fiber, a carbon fiber, or the like can beused.

As a glass fiber, a glass fiber or the like formed using E glass, Sglass, D glass, Q glass, or the like can be used.

Note that the fibrous body may be formed using only one kind of thematerials of the plurality of fibers, or may be formed using pluralkinds of the materials of the plurality of fibers.

The first insulator and the second insulator have a structure where afibrous body 400 (corresponding to the fibrous body 102 and the fibrousbody 110) is impregnated with an organic resin 401 (corresponding to theorganic resin 101 and the organic resin 109) (see FIG. 16).

An insulator formed using a fibrous body impregnated with an organicresin is also referred to as a prepreg.

Typically, a prepreg is formed as follows: after a fibrous body isimpregnated with a varnish in which a matrix resin is diluted with anorganic solvent, drying is performed so that the organic solvent isvolatilized and the matrix resin is semi-cured.

When the thickness of the prepreg is greater than or equal to 10 μm andless than or equal to 100 μm, a thin flexible semiconductor device canbe manufactured, which is preferable.

Note that each of the first insulator and the second insulator may beformed using only an organic resin which does not include a fibrousbody.

As the organic resin in this case, an epoxy resin, an unsaturatedpolyester resin, a polyimide resin, a bismaleimide triazine resin, acyanate resin, a polyphenylene oxide resin, a polyetherimide resin, afluoropolymer, or the like can be used.

Note that since the prepreg includes the fibrous body, the prepreg hashigh pulling and bending durability and a function of diffusing localpressure.

Thus, the prepreg including the fibrous body is preferably used for eachof the first insulator and the second insulator.

Further, when the first conductive film 103 and the second conductivefilm 108 are provided, static electricity locally accumulated in thefirst insulator and the second insulator can be diffused. Therefore, alarge amount of static electricity can be prevented from being locallyaccumulated and discharged.

For the first conductive film 103 and the second conductive film 108,titanium, molybdenum, tungsten, aluminum, titanium nitride, tantalumnitride, tungsten nitride, indium oxide, indium tin oxide containingsilicon oxide, or the like can be used. Note that the material for thefirst conductive film 103 and the second conductive film 108 is notlimited to the above material, and any conductive material can be usedas long as it has an effect of increasing electrostatic withstandvoltage. Note that by forming conductive films having slits, such as aplurality of island-shaped conductive films or mesh conductive films,electromagnetic waves are easily transmitted through the slits, which ispreferable. In addition, in the case where conductive films are providedon both sides, one of the conductive films is preferably formed as alight-transmitting conductive film (formed using indium oxide, indiumtin oxide containing silicon oxide, or the like) and the other of theconductive films is preferably formed as a light-blocking conductivefilm (formed using titanium, molybdenum, tungsten, aluminum, or thelike) because the difference between a front surface and a rear surfaceis easily understood. The reason for understanding the differencebetween the front surface and the rear surface is that reading ofsignals is easily performed in the case where the signals are input froma front surface side on which the antenna is provided when the signalsare input to the semiconductor device.

In the layer 105 including the circuit having the thin film transistor,the thin film transistor may have any structure as long as it functionsas a switching element. For example, either a top-gate thin filmtransistor or a bottom-gate thin film transistor may be used.

Note that instead of the thin film transistor, a switching element suchas an MIM element may be used because only the function as a switchingelement is necessary. Alternatively, a switching element formed using asilicon wafer may be used.

The first insulating film 104 is a base insulating film which isprovided below the layer 105 including the circuit having the thin filmtransistor.

By providing the base insulating film between the first conductive film103 and the layer 105 including the circuit having the thin filmtransistor, the circuit can be prevented from being short-circuited dueto electrical connection between the thin film transistors by the firstconductive film 103.

As the first insulating film 104 (the base insulating film), a siliconoxide film, a silicon nitride film, an organic resin film, or the likecan be used.

For the antenna of the layer 106 including the antenna, titanium,molybdenum, tungsten, aluminum, copper, silver, gold, nickel, platinum,palladium, iridium, rhodium, tantalum, cadmium, zinc, iron, or the likecan be used.

The shape of the antenna may be a linear shape, a curved shape, ameandering shape, a coiled shape, a ribbon shape, a shape in which theseshapes are combined with each other, or the like can be used.

Note that an antenna for electromagnetic induction, which includes twokinds of antennas, may be used.

For example, a first antenna which is electrically connected to thecircuit has a coiled shape, and a second antenna is provided over thefirst antenna with an insulating film interposed therebetween. As theinsulating film, a silicon oxide film, a silicon nitride film, anorganic resin film, or the like can be used.

As the shape of the second antenna, at least a first region having acoiled shape and a second region having a linear shape, a curved shape,a meandering shape, a ribbon shape, a shape in which these shapes arecombined with each other, or the like are provided.

Since the first region is provided in a position overlapping with thefirst antenna, signals received in the second region are supplied to thefirst antenna by electromagnetic induction.

A method by which signals are transmitted by using two kinds of antennasby electromagnetic induction in this manner is referred to as anelectromagnetic induction method.

In addition, the second insulating film 107 is a protective film of theantenna.

With the protective film, the antenna can be protected when the prepregor the like is thermally compressed.

By providing the second insulating film 107 between the secondconductive film 108 and the layer 106 including the antenna, the secondconductive film 108 and the antenna can be prevented from beingshort-circuited.

As the second insulating film 107, a silicon oxide film, a siliconnitride film, an organic resin film, or the like can be used.

Note that each of the first conductive film 103, the first insulatingfilm 104, the antenna, the second insulating film 107, and the secondconductive film 108 may have either a single-layer structure or alayered structure.

Further, by providing a buffer including aramid or the like on a singlesurface or both surfaces of each of the first insulator and the secondinsulator, resistance against pressure can be improved, which ispreferable.

In particular, by providing buffers outside the first insulator and thesecond insulator, pressure from the outside can be directly relieved,which is preferable.

By providing the first conductive film 103 and the second conductivefilm 108 as described above, electrostatic withstand voltage can beincreased.

In particular, in the case where the fibrous body is used, resistanceagainst physical force such as pressure and stress and resistanceagainst electrical force such as static electricity can be improvedsimultaneously by providing at least one film-shaped conductor (thefirst conductive film 103, the second conductive film 108, or the like).

Since the structure where at least one film-shaped conductor is providedis extremely simple, the structure can be applied to any insulator.

Thus, the application range of the structure is extremely wide.

Note that as a transformed example, a method by which a plurality ofconductive particles are contained in an organic resin used for aprepreg (a method by which conductivity is imparted inside a prepreg)can be used.

Note that since it is nearly impossible to electrically connect allfibers that are twisted intricately to each other with the plurality ofconductive particles, it might be difficult to prevent staticelectricity from being locally accumulated.

Further, since the particles and the organic resin are mixed with eachother, an insulating portion inevitably remains Thus, static electricitymight be locally accumulated in the insulating portion.

Therefore, in the structure where at least one film-shaped conductor isprovided, static electricity can be more surely prevented from beingaccumulated, which is preferable.

This is because the film-shaped conductor is provided so as to cover theentire surface, so that an effect of preventing static electricity frombeing accumulated locally is high.

This embodiment can be combined with all the other embodiments.

Embodiment 2

In this embodiment, a transformed example of Embodiment 1 is described.

As in Embodiment 1, a semiconductor device of this embodiment includes astructure where the first insulator formed using the fibrous body 102impregnated with the organic resin 101, the first conductive film 103,the first insulating film 104, the layer 105 including the circuithaving the thin film transistor, the layer 106 including the antenna,the second insulating film 107, the second conductive film 108, and thesecond insulator formed using the fibrous body 110 impregnated with theorganic resin 109 are sequentially stacked (see FIG. 2).

The structure of this embodiment differs from the structure ofEmbodiment 1 in that a conductor 111 and a conductor 112 for bringingthe first conductive film 103 and the second conductive film 108 intoconduction are provided (see FIG. 2).

Although the two conductors 111 and 112 are provided in this embodiment,the number of conductors may be one or three or more as long as thefirst conductive film 103 and the second conductive film 108 can bebrought into conduction.

By providing a conductor for bringing the first conductive film 103 andthe second conductive film 108 into conduction, a potential of the firstconductive film 103 and a potential of the second conductive film 108are kept at the same level.

Then, current can be prevented from flowing through a path interposedbetween the first conductive film 103 and the second conductive film108.

Accordingly, the circuit can be prevented from being damaged by currentin a direction perpendicular to the circuit.

This embodiment can be combined with all the other embodiments.

Embodiment 3

In this embodiment, a transformed example of Embodiment 1 or 2 isdescribed.

Any structure has an effect of increasing electrostatic withstandvoltage as long as it includes at least one film-shaped conductor. Thus,structures illustrated in FIGS. 3A to 3F can be used.

In FIGS. 3A to 3F, a first insulator 201, a layer 202 including acircuit over a base insulating film, a layer 203 including an antenna, aprotective film 204, and a second insulator 205 are sequentiallystacked.

In addition, positions where conductive films 206 to 212 are formed aredifferent in FIGS. 3A to 3F.

Note that as materials of the first insulator 201, the base insulatingfilm, the circuit, the antenna, the protective film 204, and the secondinsulator 205, the materials of the first insulator, the base insulatingfilm, the circuit, the antenna, the protective film, and the secondinsulator which are described in Embodiment 1 can be used.

In FIG. 3A, the conductive film 206 is formed outside the firstinsulator 201 and the second insulator 205 and is formed on an antennaside.

In FIG. 3B, the conductive film 207 is formed outside the firstinsulator 201 and the second insulator 205 and is formed on a thin filmtransistor side.

In FIG. 3C, the conductive film 208 is formed outside the firstinsulator 201 and the second insulator 205 and is formed on an antennaside, and the conductive film 209 is formed outside the first insulator201 and the second insulator 205 and is formed on a thin film transistorside. Note that the conductive film 208 and the conductive film 209 arenot electrically connected to each other.

In FIG. 3D, whole external surfaces of the first insulator 201 and thesecond insulator 205 are surrounded by the conductive film 210.

In FIG. 3E, the conductive film 211 is formed inside the first insulator201 and the second insulator 205 and is formed on an antenna side.

In FIG. 3F, the conductive film 212 is formed inside the first insulator201 and the second insulator 205 and is formed on a thin film transistorside.

This embodiment can be combined with all the other embodiments.

Embodiment 4

In this embodiment, an example of a method for manufacturing thesemiconductor devices described in Embodiments 1 to 3 is described.

First, over a substrate 300 (a base substrate or a substrate formanufacture of a circuit), an insulating film 301, a metal film 302, aninsulating film 303, and a first conductive film 501 are sequentiallyformed (see FIG. 4A).

As the substrate 300 (the base substrate or the substrate formanufacture of the circuit), a glass substrate, a quartz substrate, ametal substrate, a plastic substrate, or the like can be used.

As the insulating film 301, a silicon oxide film, a silicon nitridefilm, a silicon oxide film containing nitrogen, a silicon nitride filmcontaining oxygen, an aluminum nitride film, an aluminum oxide film, orthe like can be used. The insulating film 301 can be formed by CVD,sputtering, or the like. The thickness of the insulating film 301 ispreferably 10 to 500 nm. Note that the formation of the insulating film301 may be omitted.

As the metal film 302, a tungsten film, a molybdenum film, a titaniumfilm, a tantalum film, or the like can be used. The metal film 302 canbe formed by CVD, sputtering, or the like. The thickness of the metalfilm 302 is preferably 100 to 1000 nm.

As the insulating film 303, a silicon oxide film, a silicon nitridefilm, or the like can be used. The insulating film 303 can be formed byCVD, sputtering, or the like. The thickness of the insulating film 303is preferably 10 to 100 nm.

The first conductive film 501 is a conductive film for countermeasuresagainst electrostatic discharge. For the first conductive film 501,titanium, molybdenum, tungsten, aluminum, titanium nitride, tantalumnitride, tungsten nitride, indium oxide, indium tin oxide containingsilicon oxide, or the like can be used. Note that the material for thefirst conductive film 501 is not limited to the above material, and anyconductive material can be used as long as it has an effect ofincreasing electrostatic withstand voltage. The first conductive film501 can be formed by CVD, evaporation, sputtering, or the like. Thethickness of the first conductive film 501 is preferably 5 to 200 nm (or10 to 100 nm). Note that by forming conductive films having slits, suchas a plurality of island-shaped conductive films or mesh conductivefilms, electromagnetic waves are easily transmitted through the slits,which is preferable.

Note that in order to effectively prevent the semiconductor device frombeing damaged by static electricity, the sheet resistance of the firstconductive film 501 is lower than or equal to 1.0×10⁷ ohms/square,preferably lower than or equal to 1.0×10⁴ ohms/square, more preferablylower than or equal to 1.0×10² ohms/square.

Here, by sputtering a silicon target with an argon gas containingoxygen, the insulating film 303 containing silicon oxide can be formed.

In this case, a surface of the metal film 302 is oxidized with oxygen sothat a separation layer is formed. Thus, separation can be performed byphysical force in a later separation step.

Note that by sputtering the silicon target with an argon gas containingnitrogen, a surface of the metal film 302 may be nitrided so that aseparation layer is formed and the insulating film 303 may be formedusing a silicon nitride film.

Alternatively, a separation layer may be formed by performing oxygenplasma treatment or nitrogen plasma treatment on a surface of the metalfilm 302 before the insulating film 303 is formed.

In the case where oxygen plasma treatment or nitrogen plasma treatmentis performed on the surface of the metal film 302, a structure may beused in which the first conductive film 501 is formed over the metalfilm 302 without the formation of the insulating film 303.

Alternatively, instead of forming the metal film 302, a separation layerformed using silicon may be formed between the insulating film 301 andthe insulating film 303.

In the case where the separation layer formed using silicon is used, byusing halogen fluoride (e.g., chlorine fluoride (ClF), chlorinetrifluoride (ClF₃), bromine fluoride (BrF), bromine trifluoride (BrF₃),iodine fluoride (IF), or iodine trifluoride (IF₃)) in the laterseparation step, silicon is etched, so that separation can be performed.

Note that since halogen fluoride has an operation of etching silicon,metal (e.g., aluminum), or the like, the insulating film 303 has aneffect of protecting the first conductive film 501 in the case wheresilicon is used for the separation layer.

Thus, a structure may be used in which metal (e.g., aluminum) is usedfor the separation layer instead of silicon and halogen fluoride is usedas an etching material of the separation layer.

Note that in the case where a material which is not etched by halogenfluoride (e.g., an oxide conductor (indium tin oxide, indium oxidecontaining silicon oxide, or zinc oxide)) is used for the firstconductive film, the insulating film 303 is not necessarily provided.

By using a structure in which a separation layer is provided between atleast the substrate 300 and the first conductive film 501 as describedabove, the substrate 300 can be separated from the first conductive film501, a circuit provided over the first conductive film, and the like inthe later separation step.

Next, a first insulating film 304 (a base insulating film) is formed,and a thin film transistor 305 and a thin film transistor 306 are formedover the first insulating film 304 (see FIG. 4B).

The thin film transistor 305 includes a semiconductor layer 305 a, agate insulating film 305 b which is formed over the semiconductor layer305 a, a gate electrode 305 c which is formed over the gate insulatingfilm 305 b, and a sidewall 305 d and a sidewall 305 e which are formedover the gate insulating film 305 b and formed in contact with sidewallsof the gate electrode 305 c (see FIG. 4B).

The thin film transistor 306 includes a semiconductor layer 306 a, agate insulating film 306 b which is formed over the semiconductor layer306 a, a gate electrode 306 c which is formed over the gate insulatingfilm 306 b, and a sidewall 306 d and a sidewall 306 e which are formedover the gate insulating film 306 b and formed in contact with sidewallsof the gate electrode 306 c (see FIG. 4B).

Note that a plurality of thin film transistors are formed in the circuitonly as needed.

In addition, although the top-gate thin film transistors are illustratedin this embodiment, bottom-gate thin film transistors can be used.

Further, although the thin film transistors having LDD structures areillustrated, the thin film transistors do not necessarily have the LDDstructures.

Furthermore, instead of the thin film transistors, MIM elements or thelike may be used because only the functions as switching elements arenecessary.

Note that for the semiconductor layers of the thin film transistors,silicon, silicon germanium, an oxide semiconductor, an organicsemiconductor, or the like can be used.

In addition, for the gate insulating films and the sidewalls of the thinfilm transistors, silicon oxide, silicon nitride, or the like can beused.

Further, for the gate electrodes of the thin film transistors, tungsten,molybdenum, aluminum, titanium, silicon, or the like can be used.

Next, a first interlayer insulating film 307 which covers the thin filmtransistor 305 and the thin film transistor 306 is formed; a secondinterlayer insulating film 308 is formed over the first interlayerinsulating film 307; contact holes which reach the thin film transistor305 and the thin film transistor 306 are formed in the first interlayerinsulating film 307 and the second interlayer insulating film 308;wirings 309 a to 309 d which are electrically connected to the thin filmtransistor 305 and the thin film transistor 306 are formed over thesecond interlayer insulating film 308 (see FIG. 5A).

By electrically connecting the thin film transistors with the wirings,the circuit is formed.

As the first interlayer insulating film 307, a silicon oxide film, asilicon nitride film, an organic resin film, or the like can be used.The thickness of the first interlayer insulating film 307 is preferably50 to 200 nm.

As the second interlayer insulating film 308, a silicon oxide film, asilicon nitride film, an organic resin film, or the like can be used.The thickness of the second interlayer insulating film 308 is preferably300 to 5000 nm.

Note that although two interlayer insulating films are used as theinterlayer insulating films in this embodiment, a single interlayerinsulating film may be used or three or more interlayer insulating filmsmay be used.

For the wirings 309 a to 309 d, aluminum, titanium, molybdenum,tungsten, gold, silver, copper, or the like can be used. The thicknessof each of the wirings 309 a to 309 d is preferably 1000 to 5000 nm.Note that each of the wirings 309 a to 309 d may have either asingle-layer structure or a layered structure.

Next, a third interlayer insulating film 310 which covers the wirings309 a to 309 d is formed; a contact hole which reaches the wiring 309 ais formed in the third interlayer insulating film 310; a layer 311including an antenna is formed over the third interlayer insulating film310; a second insulating film 312 (a protective film) is formed over thelayer 311 including the antenna; a second conductive film 502 is formedover the second insulating film 312 (the protective film) (see FIG. 5B).

As the third interlayer insulating film 310, a silicon oxide film, asilicon nitride film, an organic resin film, or the like can be used.The thickness of the third interlayer insulating film 310 is preferably300 to 5000 nm.

For the layer 311 including the antenna, aluminum, titanium, molybdenum,tungsten, gold, silver, copper, or the like can be used. The thicknessof the layer 311 including the antenna is preferably 1000 to 5000 nm.Note that the layer 311 including the antenna may have either asingle-layer structure or a layered structure.

Note that the layer 311 including the antenna has an antenna 311 a and awiring portion 311 b.

As the second insulating film 312 (the protective film), a silicon oxidefilm, a silicon nitride film, or the like can be used. The thickness ofthe second insulating film 312 (the protective film) is preferably 100to 1000 nm.

The second insulating film 312 (the protective film) protects theantenna when a prepreg or the like is thermally compressed. In addition,the second insulating film 312 (the protective film) can prevent thesecond conductive film 502 and the layer 311 including the antenna frombeing short-circuited.

Note that the second conductive film 502 and the layer 311 including theantenna are not electrically connected to each other.

The second conductive film 502 is a conductive film for countermeasuresagainst electrostatic discharge. For the second conductive film 502,titanium, molybdenum, tungsten, aluminum, titanium nitride, tantalumnitride, tungsten nitride, indium oxide, indium tin oxide containingsilicon oxide, or the like can be used. Note that the material for thesecond conductive film 502 is not limited to the above material, and anyconductive material can be used as long as it has an effect ofincreasing electrostatic withstand voltage. The second conductive film502 can be formed by CVD, evaporation, sputtering, or the like. Thethickness of the second conductive film 502 is preferably 5 to 200 nm(or 10 to 100 nm). Note that by forming conductive films having slits,such as a plurality of island-shaped conductive films or mesh conductivefilms, electromagnetic waves are easily transmitted through the slits,which is preferable.

Note that in order to effectively prevent the semiconductor device frombeing damaged by static electricity, the sheet resistance of the secondconductive film 502 is lower than or equal to 1.0×10⁷ ohms/square,preferably lower than or equal to 1.0×10⁴ ohms/square, more preferablylower than or equal to 1.0×10² ohms/square.

Next, a first insulator in which a fibrous body 313 is impregnated withan organic resin 314 is thermally compressed over the second conductivefilm 502. Then, after the thermal compression, by application ofphysical force (pulling, pushing, or the like), a separation step ofseparating the substrate 300, the insulating film 301, and the metalfilm 302 is performed (see FIG. 6).

Since the surface of the metal film 302 is oxidized or nitrided,adhesion between the metal film 302 and the insulating film 303 is weak.

Thus, by the application of physical force, the substrate 300, theinsulating film 301, and the metal film 302 are selectively separated.

The substrate 300, the insulating film 301, and the metal film 302 maybe selectively separated by introduction of water from side surfaces.

Since water enters a separation interface by the introduction of water,a circuit side and a substrate side are electrically connected to eachother with water.

Although static electricity is generated in separation, a problem ofelectrostatic discharge in the separation is more likely to be preventedwhen the circuit side and the substrate side are electrically connectedto each other with water.

Note that in order to improve the conductivity of water, an aqueoussolution such as a saline solution or carbonated water may be used. Notethat since salt adversely affects the circuit, carbonated water ispreferable.

Note that in the case where a separation layer formed using silicon isformed instead of the metal film 302, the separation layer formed usingsilicon is selectively etched by halogen fluoride, so that the substrate300 and the insulating film 301 are selectively separated.

A step of selectively separating at least the substrate 300 by using aseparation layer is referred to as a separation step. In addition, acircuit from which a substrate is selectively separated in a separationstep is referred to as a separation circuit. Alternatively, such acircuit may be referred to as a peel circuit because only a thin circuitlike skin remains after a substrate is separated. Note that the peelcircuit may be formed by a different method such as a method for forminga peel circuit by removing a substrate with an etchant or a method forforming a peel circuit by forming a circuit over a flexible substrate.

A separation circuit (a peel circuit) including a thin film transistoris extremely thin. Thus, the circuit is extremely weak in pulling,pressure from the outside, or the like.

On the other hand, as for an insulator in which a fibrous body isimpregnated with an organic resin, the insulator has the fibrous body,so that it has high resistance against pulling and can diffuse pressurefrom the outside.

Therefore, by interposing the separation circuit (the peel circuit)including the thin film transistor between insulators in which fibrousbodies are impregnated with an organic resin, the separation circuit(the peel circuit) including the thin film transistor can be protectedagainst pulling and pressure from the outside.

Then, after the separation step, a second insulator in which a fibrousbody 315 is impregnated with an organic resin 316 is thermallycompressed below the insulating film 303 (see FIG. 7).

Note that although the prepreg illustrated in Embodiment 1 is used forthe first insulator and the second insulator, an insulator which doesnot include a fibrous body may be used in the case where the separationcircuit (the peel circuit) is not used or in the case where resistanceagainst pulling, pressure from the outside, and the like is notconsidered.

Note that by using a prepreg in the case where the separation circuit(the peel circuit) is used, a flexible semiconductor device which hasresistance against pulling, pressure from the outside, and the like canbe used, which is preferable.

In addition, by providing the first conductive film 501 and the secondconductive film 502, a semiconductor device which has high electrostaticwithstand voltage can be provided.

In particular, in the case where a prepreg having a complicated shapelike a fibrous body is used, electrostatic withstand voltage is furtherincreased in the case where a film-like conductor is provided as in thisembodiment as compared to the case where conductive particles are usedinside the prepreg.

Further, since it is necessary to form only a film in manufacturingsteps, the manufacturing steps can be simplified, which is preferable.

This embodiment can be combined with all the other embodiments.

Embodiment 5

In this embodiment, a transformed example of Embodiment 4 is described.

After the step of FIG. 5A, the third interlayer insulating film 310which covers the wirings 309 a to 309 d is formed; the contact holewhich reaches the wiring 309 a is formed in the third interlayerinsulating film 310; the layer 311 including the antenna is formed overthe third interlayer insulating film 310; the second insulating film 312(the protective film) is formed over the layer 311 including theantenna; a contact hole which reaches the first conductive film 501 isformed in a position where the layer 311 including the antenna and thethin film transistor are not formed; a conductor 317 is embedded in thecontact hole (see FIG. 8A).

For the conductor 317, aluminum, titanium, molybdenum, tungsten, gold,silver, copper, or the like can be used. As an embedding method, amethod can be used by which after a conductive film is formed to athickness which is larger than the depth of the contact hole, etching isperformed by etch back, chemical mechanical polishing (CMP), or the likeso that a surface of the protective film is exposed.

Note that although the number of portions where the first conductivefilm 501 and the second conductive film 502 are in contact with eachother is only one in FIGS. 8A and 8B, the number of portions where thefirst conductive film 501 and the second conductive film 502 are incontact with each other may be plural.

Note that the portions where the first conductive film 501 and thesecond conductive film 502 are in contact with each other are located inthe position where the layer 311 including the antenna and the thin filmtransistor are not formed.

Next, the second conductive film 502 which is electrically connected tothe conductor 317 is formed over the second insulating film 312.

Next, the first insulator in which the fibrous body 313 is impregnatedwith the organic resin 314 is thermally compressed over the secondconductive film 502. Then, after the thermal compression, by applicationof physical force (pulling, pushing, or the like), a separation step ofseparating the substrate 300, the insulating film 301, and the metalfilm 302 is performed (see FIG. 9).

Then, after the separation step, the second insulator in which thefibrous body 315 is impregnated with the organic resin 316 is thermallycompressed below the insulating film 303 (see FIG. 10).

By using a structure where the first conductive film 501 and the secondconductive film 502 are electrically connected to each other asdescribed above, a potential of the first conductive film 501 and apotential of the second conductive film 502 are kept at the same level,so that electrostatic withstand voltage can be raised.

Note that the first conductive film 501 and the second conductive film502 may be in contact with each other by using the second conductivefilm 502 without the formation of the conductor 317. Alternatively,after the second conductive film 502 is formed, the first conductivefilm 501 and the second conductive film 502 may be irradiated with laserlight so as to be melted and be in contact with each other.

This embodiment can be combined with all the other embodiments.

Embodiment 6

Although the second conductive film is provided over the antenna inEmbodiments 4 and 5, the second conductive film may be provided betweenthe antenna and the circuit including the thin film transistor.

Specifically, a third conductive film 503 having an opening portion isprovided over the third interlayer insulating film 310. A fourthinterlayer insulating film 318 is formed over the third conductive film503 so that the antenna and the third conductive film 503 are notshort-circuited (see FIG. 11).

Note that the opening portion in the third conductive film 503 is largerthan a contact hole provided in the fourth interlayer insulating film318 so that the antenna and the third conductive film 503 are notshort-circuited.

As the material of the fourth interlayer insulating film 318, a siliconoxide film, a silicon nitride film, an organic resin film, or the likecan be used.

With the above structure, a conductive film which blocks the antenna isnot provided. Thus, a problem of deviation of resonant frequency due tothe conductive film can be prevented.

Note that in a manner similar to that of Embodiment 5, the firstconductive film 501 and the third conductive film 503 may beelectrically connected to each other through the contact hole.

Further, the material of the third conductive film 503 is similar tothose of the first conductive film 501 and the second conductive film502.

This embodiment can be combined with all the other embodiments.

Embodiment 7

Although the conductive films for countermeasures against electrostaticdischarge are provided inside the first insulator and the secondinsulator in Embodiments 4 to 6, the conductive films forcountermeasures against electrostatic discharge may be provided outsidethe first insulator and the second insulator.

Specifically, a fourth conductive film 504 is formed on a bottom surfaceof the second insulator in which the fibrous body 315 is impregnatedwith the organic resin 316, and a fifth conductive film 505 is formed ona top surface of the first insulator in which the fibrous body 313 isimpregnated with the organic resin 314 (see FIG. 12).

As for a formation method, thermal compression may be performed afterthe conductive films are formed on the surfaces of the first insulatorand the second insulator, or the conductive films may be formed afterthermal compression is performed.

In addition, the fourth conductive film 504 and the fifth conductivefilm 505 may be electrically connected to each other so as to be a sixthconductive film 506 (see FIG. 13).

As for a method for electrically connecting the fourth conductive film504 and the fifth conductive film 505 to each other, conductive filmsmay be formed on side surfaces, or the fourth conductive film 504 andthe fifth conductive film 505 may be irradiated with laser light so asto be melted and be in contact with each other.

Further, the materials of the fourth to sixth conductive films aresimilar to those of the first conductive film 501 and the secondconductive film 502.

This embodiment can be combined with all the other embodiments.

Embodiment 8

In order to improve an effect of increasing electrostatic withstandvoltage, it is effective to lower the resistance value of a conductivefilm.

In order to lower the resistance value of the conductive film, thethickness of the conductive film is simply made larger.

However, if the thickness of a conductive film of an antenna is madelarger, resonant frequency is deviated, so that communication distanceis decreased.

Thus, as a transformed example of FIG. 13, a seventh conductive film 507is formed in a position which does not overlap with the antenna 311 a.Note that the seventh conductive film 507 and the wiring portion 311 bmay be provided in a position where they overlap with each other, or maybe provided in a position where they do not overlap with each other (seeFIG. 14).

With the structure of FIG. 14, deviation of resonant frequency in anantenna region can be kept to the minimum and an effect of increasingelectrostatic withstand voltage can be improved.

Note that the thickness of the seventh conductive film 507 is preferablylarger than that of the sixth conductive film 506.

In addition, an eighth conductive film 508 which has a shape where theconductive film provided in the position which overlaps with the antenna311 a is removed may be provided (see FIG. 15).

As a formation method of the seventh and eighth conductive films, amethod by which a pattern is formed using a metal mask in deposition, amethod by which a mask is formed by photolithography or the like after aconductive film is formed over the entire surface and then part of theconductive film is selectively removed, or the like can be used.

Further, the materials of the seventh and eighth conductive films aresimilar to those of the first conductive film 501 and the secondconductive film 502. Note that although an example in which theconductive films are provided outside the insulators is illustrated inthis embodiment, the structure of this embodiment may be used after theconductive films are provided inside the insulators. Furthermore, byforming a plurality of island-shaped conductive films, mesh conductivefilms, or the like as the conductive film provided in the region whichoverlaps with the antenna, electromagnetic waves are easily transmittedthrough slits, and conductive films may be provided over the entiresurface in the other regions.

This embodiment can be combined with all the other embodiments.

Embodiment 9

An example where an impact diffusion layer is provided in Embodiments 1to 8 is illustrated.

For the impact diffusion layer, an aramid resin, a polyethylenenaphthalate (PEN) resin, a polyether sulfone (PES) resin, apolyphenylene sulfide (PPS) resin, a polyimide (PI) resin, or the likecan be used.

The impact diffusion layer is preferably provided so as to be in contactwith surfaces of the outside of the first insulator and the secondinsulator.

That is, with the structure, the impact diffusion layer is exposed, sothat external pressing force durability is improved.

Note that in the case of a structure as in FIG. 12 or FIG. 13, theimpact diffusion layer may be provided between a conductive film and aninsulator, or may be provided on a surface of the outside of theconductive film.

In particular, when the impact diffusion layer is provided on thesurface of the outside of the conductive film, the impact diffusionlayer is exposed and the conductive film is not exposed.

Then, since the conductive film is protected against friction or thelike with the impact diffusion layer, the conductive film can beprevented from being peeled due to friction, which is preferable.

As for a formation method, thermal compression may be performed afterthe impact diffusion layer is formed on the surfaces of the firstinsulator and the second insulator, or the impact diffusion layer may beformed after thermal compression is performed.

Note that in the case where the impact diffusion layer is provided onthe surface of the conductive film, the impact diffusion layer may beprovided after the conductive film is formed.

The impact diffusion layer can be provided by thermal compression or thelike. A film-shaped impact diffusion layer may be attached by using anadhesive.

This embodiment can be combined with all the other embodiments.

Embodiment 10

In this embodiment, examples of a circuit of a semiconductor device andoperation thereof are described.

A semiconductor device 800 which has a function of communicating datawithout contact includes a high-frequency circuit 810, a power supplycircuit 820, a reset circuit 830, a clock generation circuit 840, a datademodulation circuit 850, a data modulation circuit 860, a controlcircuit 870 which controls another circuit, a memory circuit 880, and anantenna 890 (see FIG. 18).

The high-frequency circuit 810 is a circuit which receives a signal fromthe antenna 890 and outputs a signal received from the data modulationcircuit 860 from the antenna 890.

The power supply circuit 820 is a circuit which generates a power supplypotential from a received signal.

The reset circuit 830 is a circuit which generates a reset signal 831.

The clock generation circuit 840 is a circuit which generates a varietyof clock signals 841 in accordance with a received signal which is inputfrom the antenna 890.

The data demodulation circuit 850 is a circuit which demodulates areceived signal and outputs the demodulated signal 851 to the controlcircuit 870.

The data modulation circuit 860 is a circuit which modulates a signalreceived from the control circuit 870.

In addition, the control circuit 870 includes, for example, a codeextraction circuit 910, a code determination circuit 920, a CRCdetermination circuit 930, and an output unit circuit 940.

Note that the code extraction circuit 910 is a circuit which extractseach of a plurality of codes included in an instruction transmitted tothe control circuit 870.

The code determination circuit 920 is a circuit which determines thecontent of an instruction by comparing an extracted code with a codewhich corresponds to a reference.

The CRC determination circuit 930 is a circuit which detects thepresence or absence of a transmission error or the like in accordancewith a determined code.

Next, an example of the operation of the above semiconductor device isdescribed.

First, a radio signal is received by the antenna 890.

The radio signal is transmitted to the power supply circuit 820 throughthe high frequency circuit 810, and a high power supply potential(hereinafter referred to as VDD 821) is generated.

The VDD 821 is applied to each circuit included in the semiconductordevice 800.

In addition, a signal transmitted to the data demodulation circuit 850through the high frequency circuit 810 is demodulated, which is referredto as a demodulated signal.

Further, signals passed through the reset circuit 830 and the clockgeneration circuit 840 through the high-frequency circuit 810, and thedemodulated signal are transmitted to the control circuit 870.

The signals transmitted to the control circuit 870 are analyzed by thecode extraction circuit 910, the code determination circuit 920, the CRCdetermination circuit 930, and the like.

Then, based on the analyzed signals, information in the semiconductordevice, which is stored in the memory circuit 880, is output.

The information in the semiconductor device, which is output, is encodedthrough the output unit circuit 940.

Further, the information in the semiconductor device 800, which isencoded, passes through the data modulation circuit 860 and then istransmitted by the antenna 890 as a wireless signal.

Note that a low power supply potential (hereinafter referred to as VSS)is common in the plurality of circuits included in the semiconductordevice 800, and the VSS can be set to GND.

This embodiment can be combined with all the other embodiments.

Embodiment 11

The semiconductor devices for performing wireless communication throughantennas (also referred to as RFID tags, wireless tags, IC chips,wireless chips, noncontact signal processing devices, or semiconductorintegrated circuit chips) in Embodiments 1 to 10 can be attached tosurfaces of products or living things (e.g., human beings, animals, orplants) or can be embedded inside products or living things (e.g., humanbeings, animals, or plants), for example.

By using the semiconductor device for performing wireless communicationthrough the antenna, information management without contact becomespossible.

Communication of data without contact leads to an environment whereusers can utilize an information communication technology at any timeand anywhere (ubiquitous computing).

This embodiment can be combined with all the other embodiments.

Example 1

In order to demonstrate an effect of countermeasures againstelectrostatic discharge, measurement of ESD (electrostatic discharge)was performed.

The measurement of ESD was performed as follows.

First, an aluminum plate was put on a glass substrate (0.5-nm-thick).Then, a conductive sheet was put on the aluminum plate, and a sample wasput on the conductive sheet.

Then, from above the sample (chip), predetermined voltage was applied byusing an ESD tester (manufactured by TAKAYA Corporation, for evaluatingsimple response).

Next, electricity of the sample (chip) to which the predeterminedvoltage was applied was removed for one minute.

After that, whether or not the sample (chip) from which the electricitywas removed operated was determined.

Then, by increasing the predetermined voltage from 1 kV to 15 kV,voltage at which the sample (chip) was not able to operate was measured.

In addition, the measurement was performed in two cases: the case wherevoltage was applied from a front surface (an antenna side) of the sample(chip) and the case where voltage was applied from a rear surface (athin film transistor side) of the sample (chip).

Note that it was determined that a sample (chip) which operated after avoltage of 15 kV was applied had at least an electrostatic withstandvoltage of 15 kV or higher.

Here, the sample on which the measurement was performed is described.

(A Comparison Structure: A Structure where a Conductive Film forCountermeasures Against Electrostatic Discharge is not Provided)

As a comparison structure, a structure was used in which a firstinsulator 11, a circuit 12 including a thin film transistor providedover the first insulator 11, an antenna 13 which is provided over thecircuit 12 including the thin film transistor and is electricallyconnected to the circuit 12 including the thin film transistor, aprotective film 14 (a silicon nitride film) provided over the antenna13, and a second insulator 15 provided over the protective film 14 wereprovided (see FIG. 17A).

In the comparison structure, a conductive film for countermeasuresagainst electrostatic discharge was not provided.

Note that as each of the first insulator and the second insulator, aprepreg (20-μm-thick) which was a structural body in which a fibrousbody (a glass fiber) was impregnated with an organic resin (a brominatedepoxy resin) was used.

Samples which were manufactured are described below.

(First Structure: A Structure where a Conductive Film forCountermeasures Against Electrostatic Discharge is Provided on Only aFront Surface Side (an Antenna Side))

As a first structure, a structure was used in which a conductive film 16for countermeasures against electrostatic discharge was provided on onlya front surface side (an antenna side) of the comparison structure (seeFIG. 17B).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of the firststructure were the same as those of the comparison structure.

A sample in which a 10-nm-thick titanium (Ti) film was formed as theconductive film was formed.

(Second Structure: A Structure where a Conductive Film forCountermeasures Against Electrostatic Discharge is Provided on Only aRear Surface Side (a Thin Film Transistor Side))

As a second structure, a structure was used in which a conductive film17 for countermeasures against electrostatic discharge was provided ononly a rear surface side (a thin film transistor side) of the comparisonstructure (see FIG. 17C).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of thesecond structure were the same as those of the comparison structure.

A sample in which a 10-nm-thick titanium (Ti) film was formed as theconductive film was formed.

(Third Structure: A Structure where Conductive Films for CountermeasuresAgainst Electrostatic Discharge are Provided on a Front Surface Side (anAntenna Side) and a Rear Surface Side (a Thin Film Transistor Side)(Conduction Between the Top and the Bottom is not Provided))

As a third structure, a structure was used in which a conductive film 18and a conductive film 19 for countermeasures against electrostaticdischarge were provided on a front surface side (an antenna side) and arear surface side (a thin film transistor side) of the comparisonstructure (see FIG. 17D).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of the thirdstructure were the same as those of the comparison structure.

Note that the conductive film on the front surface side (the antennaside) and the conductive film on the rear surface side (the thin filmtransistor side) were electrically isolated from each other.

A sample in which a 10-nm-thick titanium (Ti) film was formed as theconductive film and a sample in which a 10-nm-thick indium tin oxide(ITO (containing SiO₂)) film containing silicon oxide was formed as theconductive film were formed.

(Fourth Structure: A Structure where Conductive Films forCountermeasures Against Electrostatic Discharge are Provided on a FrontSurface Side (an Antenna Side) and a Rear Surface Side (a Thin FilmTransistor Side) (Conduction Between the Top and the Bottom isProvided))

As a fourth structure, by providing conductive films for countermeasuresagainst electrostatic discharge on a front surface side (an antennaside) and a rear surface side (a thin film transistor side) of thecomparison structure and electrically connecting the conductive films toeach other, a structure was used in which the first insulator 11, thecircuit 12 including the thin film transistor, the antenna 13, theprotective film 14, and the second insulator 15 were surrounded by aconductive film 20 (see FIG. 17E).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of thefourth structure were the same as those of the comparison structure.

Note that the conductive film on the front surface side (the antennaside) and the conductive film on the rear surface side (the thin filmtransistor side) were electrically connected to each other.

A sample in which a 10-nm-thick titanium (Ti) film was formed as theconductive film, a sample in which a 10-nm-thick indium tin oxide (ITO(containing SIO₂)) film containing silicon oxide was formed as theconductive film, and a sample in which a 100-nm-thick indium tin oxide(ITO (containing SiO₂)) film containing silicon oxide was formed as theconductive film were formed.

(Fifth Structure: A Structure where Conductive Films for CountermeasuresAgainst Electrostatic Discharge are Provided on a Front Surface Side (anAntenna Side) and a Rear Surface Side (a Thin Film Transistor Side) ofthe Inside of an Insulator)

As a fifth structure, a structure was used in which conductive films 21and 22 for countermeasures against electrostatic discharge were providedinside the insulator of the comparison structure. Specifically, theconductive film 21 was provided between the first insulator and thecircuit including the thin film transistor, and the conductive film 22was provided between the second insulator and the protective film (seeFIG. 17F).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of the fifthstructure were the same as those of the comparison structure.

Note that the conductive film on the front surface side (the antennaside) and the conductive film on the rear surface side (the thin filmtransistor side) were electrically connected to each other.

A sample in which a 10-nm-thick indium tin oxide (ITO (containing SiO₂))film containing silicon oxide was formed as the conductive film wasformed.

(Sixth Structure: A Structure where a Conductive Film forCountermeasures Against Electrostatic Discharge is Provided on Only aFront Surface Side (an Antenna Side) of the Inside of an Insulator)

As a sixth structure, a structure was used in which a conductive film 23for countermeasures against electrostatic discharge was provided insidethe insulator of the comparison structure. Specifically, the conductivefilm 23 was provided between the second insulator and the protectivefilm (see FIG. 17G).

The structure of a thin film transistor, the structure of a circuit, theshape of an antenna, a manufacturing material, and the like of the sixthstructure were the same as those of the comparison structure.

A sample in which a 10-nm-thick indium tin oxide (ITO (containing SiO₂))film containing silicon oxide was formed as the conductive film wasformed.

(Measurement Results and Consideration)

The measurement results of the comparison structure and the first tosixth structures are illustrated in FIG. 19.

Note that the result of the comparison structure is an average value offour samples. The result of each of the first to sixth structures is anaverage value of five samples.

When the result of the comparison structure and the result of each ofthe first to sixth structures are compared with each other, it is foundthat electrostatic withstand voltage is increased with respect toapplication of voltage from a surface on which a conductive film forcountermeasures against electrostatic discharge is provided.

Therefore, it is clear that electrostatic withstand voltage is increasedby providing a conductive film.

Thus, in the case of a semiconductor device which can transmit andreceive radio waves to and from opposite surfaces like an IC card,conductive films are preferably provided on both a front surface and arear surface.

Needless to say, since there is an effect of increasing electrostaticwithstand voltage even in the case where a conductive film is providedon only a single surface, the present invention is not limited to thecase where conductive films are provided on both a front surface and arear surface.

In addition, from the measurement results of the comparison structure(FIG. 17A), the first structure (FIG. 17B), and the sixth structure(FIG. 17G), it can be understood that each chip has lower electrostaticwithstand voltage on the rear surface side (the thin film transistorside).

The reason for this is that the chip cannot operate because the thinfilm transistor or a wiring used for the circuit is damaged by staticelectricity.

Therefore, in the case where a conductive film is provided on only asingle surface, the conductive film is preferably provided on the rearsurface side (the thin film transistor side).

In addition, from the measurement results of the comparison structure(FIG. 17A), the fifth structure (FIG. 17F), and the sixth structure(FIG. 17G), it can be understood that there is an effect of increasingelectrostatic withstand voltage even in the case where a conductive filmis provided inside an insulator.

Further, since each of the indium tin oxide film containing siliconoxide and the titanium film has an effect of increasing electrostaticwithstand voltage, it can be understood that any conductive film has aneffect of increasing electrostatic withstand voltage regardless ofmaterials.

Furthermore, in the fourth structure (FIG. 17E), an effect of increasingelectrostatic withstand voltage is further improved in the case wherethe thickness of the conductive is made larger (in the case where theresistance value of the conductive film is made lower).

Therefore, it can be understood that an effect of increasingelectrostatic withstand voltage is further improved in the case wherethe resistance value of the conductive film is lower.

In addition, the electrostatic withstand voltage of the fourth structure(FIG. 17E) and the fifth structure (FIG. 17F) is extremely higher thanthat of the other structures. The average of the electrostatic withstandvoltage of the other structures is in the single digits (lower than 10kV); however, the average of the electrostatic withstand voltage of thestructures 4 and 5 is in the two digits (higher than 10 kV).

This point can be explained by consideration of dielectric polarization.

That is, each sample of this example includes the first insulator andthe second insulator.

Thus, since dielectric polarization is generated when one of surfaces ofthe first insulator or the second insulator is charged, the other of thesurfaces is charged to polarity opposite to that of the one of thesurfaces.

Then, since current flows to the circuit provided between the firstinsulator and the second insulator when dielectric polarization isgenerated, the circuit is damaged by static electricity in some cases.

On the other hand, with a structure in which a conductive film on afront surface and a conductive film on a rear surface are electricallyconnected to each other like the fourth structure (FIG. 17E) and thefifth structure (FIG. 17F), a potential of the conductive film on thefront surface and a potential of the conductive film on the rear surfaceare kept at the same level.

Thus, in the structure in which the conductive film on the front surfaceand the conductive film on the rear surface are electrically connectedto each other, even when one of surfaces of the first insulator or thesecond insulator is charged, the other of the surfaces is charged to thesame potential as the one of the surfaces.

Therefore, since an adverse effect of electrostatic discharge due todielectric polarization can be reduced in the fourth structure (FIG.17E) and the fifth structure (FIG. 17F), electrostatic withstand voltageis further increased as compared to the other structures.

Note that needless to say, the present invention is not limited to thestructures of this example.

Note that in the fourth structure, all the peripheral surfaces aresurrounded by the conductive film, as illustrated in FIG. 17E; however,it is clear from the results of this example that any structure canreduce an adverse effect of dielectric polarization as long as it is astructure in which a conductive film on a front surface and a conductivefilm on a rear surface are electrically connected to each other.

As described above, the present inventors were able to obtain novelfindings from the experimental results of this example.

Example 2

In Example 1, it is described that an effect of increasing electrostaticwithstand voltage is improved by making the thickness of the conductivefilm larger.

On the other hand, change in resonant frequency of the circuit due toincrease in thickness of the conductive film is a concern.

That is, a wireless chip operates by input of a radio wave havingcertain frequency from the outside.

In addition, when the resonant frequency of the circuit is similar tothe frequency of a radio wave which is input from the outside, thewireless chip easily operates.

On the other hand, when the resonant frequency of the circuit is notsimilar to the frequency of a radio wave which is input from theoutside, the wireless chip does not easily operate.

Further, the resonant frequency can be set by a designer in accordancewith the number of winding of the antenna or circuit design.

Accordingly, by providing the conductive film, if actual resonantfrequency deviates from resonant frequency which is set by the designer,the performance of the wireless chip is decreased.

Thus, in this example, an adverse effect on resonant frequency due todifference in thickness of a conductive film was examined.

As samples, the sample of the comparison structure in Example 1, thesample in which the 10-nm-thick indium tin oxide (ITO (containing SiO₂))film containing silicon oxide was formed in the fourth structure (FIG.17E) in Example 1, and the sample in which the 100-nm-thick indium tinoxide (ITO (containing SiO₂)) film containing silicon oxide was formedin the fourth structure in Example 1 were formed.

Note that the samples were formed so that structures other than thestructures and the thickness of the conductive films were all the same.

Measurement results are as follows.

In the sample of the comparison structure (FIG. 17A) where theconductive film is not provided, resonant frequency was 15.5 MHz.

In the sample where the thickness of the conductive film is 10 nm in thefourth structure (FIG. 17E), resonant frequency was 14.3 MHz.

In the sample where the thickness of the conductive film is 100 nm inthe fourth structure (FIG. 17E), resonant frequency was 13.0 MHz.

From the above results, it was found that as the thickness of theconductive film became larger, deviation of resonant frequency becamelarger.

From the results of this example, in order to improve an effect ofpreventing electrostatic discharge and to reduce an adverse effect ofresonant frequency, a structure was came up in which the thickness of aconductive film in a region overlapping with an antenna is made smallerthan those of conductive films in the other regions (see FIG. 14).

Alternatively, the conductive film in the region overlapping with theantenna may be removed (see FIG. 15).

Note that in the case where the conductive film is removed, electriccharge is more likely to be accumulated in the region locally. Thus, asillustrated in FIG. 14, a thin conductive film is preferably provided inthe region overlapping with the antenna.

Alternatively, a conductive film may be provided between the antenna andthe circuit including the thin film transistor (see FIG. 11).

This application is based on Japanese Patent Application serial no.2008-239078 filed with Japan Patent Office on Sep. 18, 2008 and JapanesePatent Application serial no. 2008-239075 filed with Japan Patent Officeon Sep. 18, 2008, the entire contents of which are hereby incorporatedby reference.

1. A semiconductor device comprising: a first insulator; a circuitincluding a thin film transistor over the first insulator; an antennaover the circuit and electrically connected to the circuit; and a secondinsulator over the antenna, wherein a first conductive film is providedbetween the first insulator and the circuit, and wherein a secondconductive film is provided between the second insulator and theantenna.
 2. The semiconductor device according to claim 1, wherein eachof the first insulator and the second insulator has a structure in whicha fibrous body is impregnated with an organic resin.
 3. Thesemiconductor device according to claim 1, wherein the first conductivefilm and the second conductive film are electrically connected to eachother.
 4. The semiconductor device according to claim 1, wherein thefirst insulator has a structure in which a fibrous body is impregnatedwith an organic resin, and the organic resin comprises a materialselected from the group consisting of epoxy resin, unsaturated polyesterresin, polyimide resin, bismaleimide triazine resin, cyanate resin,polyphenylene oxide resin, polyetherimide resin and fluoropolymer. 5.The semiconductor device according to claim 1, wherein the firstinsulator has a structure where a fibrous body is impregnated with anorganic resin, and the fibrous body comprises a material selected fromthe group consisting of polyvinyl alcohol fiber, polyester fiber,polyamide fiber, polyethylene fiber, aramide fiber, polyparaphenylenebenzobisoxazole fiber, glass fiber and carbon fiber.
 6. Thesemiconductor device according to claim 1, wherein the second insulatorhas a structure where a fibrous body is impregnated with an organicresin, and the organic resin comprises a material selected from thegroup consisting of epoxy resin, unsaturated polyester resin, polyimideresin, bismaleimide triazine resin, cyanate resin, polyphenylene oxideresin, polyetherimide resin and fluoropolymer.
 7. The semiconductordevice according to claim 1, wherein the second insulator has astructure where a fibrous body is impregnated with an organic resin, andthe fibrous body comprises a material selected from the group consistingof polyvinyl alcohol fiber, polyester fiber, polyamide fiber,polyethylene fiber, aramide fiber, polyparaphenylene benzobisoxazolefiber, glass fiber and carbon fiber.
 8. The semiconductor deviceaccording to claim 1, wherein the antenna comprises a material selectedfrom the group consisting of titanium, molybdenum, tungsten, aluminum,copper, silver, gold, nickel, platinum, palladium, iridium, rhodium,tantalum, cadmium, zinc and iron.
 9. A semiconductor device comprising:a first insulator; a circuit including a thin film transistor providedover the first insulator; an antenna which is provided over the circuitand is electrically connected to the circuit; and a second insulatorprovided over the antenna, wherein a first conductive film is providedbetween the first insulator and the circuit, and wherein a secondconductive film is provided between the circuit and the antenna.
 10. Thesemiconductor device according to claim 9, wherein each of the firstinsulator and the second insulator has a structure where a fibrous bodyis impregnated with an organic resin.
 11. The semiconductor deviceaccording to claim 9, wherein the first conductive film and the secondconductive film are electrically connected to each other.
 12. Thesemiconductor device according to claim 9, wherein the first insulatorhas a structure where a fibrous body is impregnated with an organicresin, and the organic resin comprises a material selected from thegroup consisting of epoxy resin, unsaturated polyester resin, polyimideresin, bismaleimide triazine resin, cyanate resin, polyphenylene oxideresin, polyetherimide resin and fluoropolymer.
 13. The semiconductordevice according to claim 9, wherein the first insulator has a structurewhere a fibrous body is impregnated with an organic resin, and thefibrous body comprises a material selected from the group consisting ofpolyvinyl alcohol fiber, polyester fiber, polyamide fiber, polyethylenefiber, aramide fiber, polyparaphenylene benzobisoxazole fiber, glassfiber and carbon fiber.
 14. The semiconductor device according to claim9, wherein the second insulator has a structure where a fibrous body isimpregnated with an organic resin, and the organic resin comprises amaterial selected from the group consisting of epoxy resin, unsaturatedpolyester resin, polyimide resin, bismaleimide triazine resin, cyanateresin, polyphenylene oxide resin, polyetherimide resin andfluoropolymer.
 15. The semiconductor device according to claim 9,wherein the second insulator has a structure where a fibrous body isimpregnated with an organic resin, and the fibrous body comprises amaterial selected from the group consisting of polyvinyl alcohol fiber,polyester fiber, polyamide fiber, polyethylene fiber, aramide fiber,polyparaphenylene benzobisoxazole fiber, glass fiber and carbon fiber.16. The semiconductor device according to claim 9, wherein the antennacomprises a material selected from the group consisting of titanium,molybdenum, tungsten, aluminum, copper, silver, gold, nickel, platinum,palladium, iridium, rhodium, tantalum, cadmium, zinc and iron. 17-26.(canceled)